Method and apparatus for tissue expansion

ABSTRACT

Exemplary embodiments of the present disclosure provide method and apparatus for facilitating stretching of a biological tissue by forming a plurality of micro-slits in the tissue. Each micro-slit can be less than about 2 mm or less than about 1.5 mm long, or even less than about 1 mm, such that small gaps that can heal quickly can be formed when the tissue is stretched. The micro-slits can be formed using a plurality of cutting arrangements or an ablative laser. The micro-slits can be formed in various patterns, including staggered rows, circular or spiral patterns, or random patterns.

CROSS REFERENCE TO RELATED APPLICATION

The present application is a divisional of U.S. patent application Ser.No. 15/677,935 filed Aug. 15, 2017, which is a continuation of U.S.patent application Ser. No. 12/936,161 filed on May 20, 2012, whichclaims priority from International Patent Application No.PCT/US2009/039125 filed Apr. 1, 2009 and from U.S. Provisional PatentApplication Ser. No. 61/041,591 filed Apr. 1, 2008, the disclosures ofwhich are incorporated herein by reference in their entireties.

FIELD OF THE DISCLOSURE

The present disclosure relates to an expansion of biological tissue, andin particular to exemplary embodiments of method and apparatus which canprovide such expansion.

BACKGROUND INFORMATION

Expansion of connective tissue, especially skin, fascia, cartilage andtendon, is often desirable for cosmetic or functional purposes.Achieving tissue expansion without damaging, impairing, or aestheticallyharming the tissue is a common concern in reconstruction after surgery,trauma, and for various medical and congenital disorders. Tissueexpansion can be used for tension relief of contracted surgical,traumatic, and burn scars. For example, burn victims often sufferthrough many painful surgeries performed to relieve the tension andcontraction of hypertrophic scars. After excision of skin cancer on theforehead and scalp, large defects are often left to heal openly becausethe surrounding skin cannot be moved enough to close the wound. On thelegs, skin healing can be poor and the skin is relatively inelastic,such that surgical wounds and ulcers on the legs are difficult to close.Scalp reduction surgery can be limited by the rigidity of scalp skin. Inaddition to a need for tissue stretching of skin in these examples,tissue stretching can also be useful for lengthening tendons, re-shapingcartilage, and for expanding other connective tissues.

Conventional techniques for stretching tissue include, e.g., (a)subcutaneous implantation of saline-filled balloons to expand the skinprior to surgery, (b) using incisions to create various artful flapsthat move skin from one location to another without removing itentirely, such that tension is relieved and/or missing tissue isreplaced by mobilizing the surrounding tissue, and (c) tissue grafts,which involve removal of skin or other connective tissue from onelocation and placing it on another location. Tissue grafts can be usedto replace skin or other tissue that has been removed by surgery ortrauma. For example, split-thickness skin grafts can be used to cover awound in burn and skin ulcer patients. A conventional split-thicknessgraft can be made, e.g., by harvesting a sheet of epidermis and upperdermis tissue from a donor site, much like peeling an apple, which canthen be placed on the burn or ulcer location. The skin tissue can thengrow back on the donor site following a generally extended healing time.

Split thickness grafts may often be “meshed” for expansion, so they cancover a larger area than the donor site. Conventional tissue meshingincludes formation of an array of many slits, typically severalmillimeters in length or longer, which can open into diamond-shaped orlens-shaped holes when the meshed graft is subjected to tension andexpanded. These holes can facilitate an overall expansion of the graft.The expanded meshed tissue sheet generally may have an appearance of achain-link fence, with large holes that can remain visible after thegraft is placed and the tissue is healed. Thus, meshed grafts may save aburn victim's life by expanding the usable area of skin available fromdonor sites, but they also can contribute to life-long aestheticdisfigurement.

Conventional full-thickness grafts generally include a removal ofepidermal tissue and the complete thickness of the dermis from a donorsite to be used as a graft, with the edges of skin adjacent to theremoved tissue being re-opposed at the donor site. Meshing may not beideal for expanding full-thickness grafts because, for example, (a) thelens-shaped holes left by gross meshing and expansion of full-thicknessskin can be even more disfiguring than in split-thickness grafts becausethey are much deeper, and may look like an array of acne scars afterhealing, and (b) the large, full-thickness holes can take weeks to healbecause cells from the surrounding dermis have to build new fibrotictissue to fill in the substantial volume of each hole. Similarly,meshing of flaps may not be appropriate because skin incisions within aflap can sever some of the blood supply to the flap, thus impairing theviability of the flap tissue. For these reasons, conventional tissuemeshing may generally not be suitable for expansion of skin grafts orflaps during surgery, and not for relief of tension on scars, nor tomodify the scar tissue itself.

Accordingly, there can be a need to address and/or overcome at leastsome of the deficiencies or issues described herein above.

SUMMARY OF EXEMPLARY EMBODIMENTS

Embodiments of the present disclosure are directed to method andapparatus for facilitating an expansion of a portion of tissue, whilereducing a presence or likelihood of noticeable holes or scars afterhealing of the expanded tissue. The exemplary method and apparatus canbe applied in situ for releasing local skin tension, to cover damaged orremoved regions of tissue using adjacent healthy tissue, and othertissue expansion applications, or ex vivo for expansion ofsplit-thickness and/or full thickness grafts while providing an improvedoutcome.

According to one exemplary embodiment of the present disclosure, amethod can be provided for facilitating tissue expansion that includes aformation of a plurality of micro-slits in the tissue to be stretched.The length of extension of the micro-slits can be less than about 2 mm,or less than about 1.5 mm, or less than about 1 mm, or even less thanabout 0.8 mm. The length of each micro-slit can be greater than about0.1 mm to allow sufficient expansion of the tissue. The width of the gapformed by a micro-slit when the tissue is expanded can be less thanabout 1 mm, or preferably less than about 0.5 mm.

Such micro-slits may extend through an entire depth of the tissue (e.g.,in a full-thickness graft or a split-thickness graft), or to aparticular depth such as, e.g., the depth of the dermis (e.g., for insitu meshing and stretching). A force can then be applied to the tissueto expand it, which can widen the micro-slits to form lens-shaped orrounded gaps therefrom. The small dimensions of the micro-slits—and thegaps formed therefrom after stretching—can facilitate rapid regrowth andfilling of these gaps, which can be facilitated by adjacent functionaltissue. A shallower depth can also be formed, e.g., a depth of about 0.6mm in skin tissue, or about one-third (⅓) of the skin thickness, whichcan assist in avoiding formation of scars after the tissue is stretchedand allowed to heal. Accordingly, the use of such micro-slits can reducehealing times and result in an aesthetically pleasing appearance of thestretched tissue.

In certain exemplary embodiments of the present disclosure, micro-slitscan be provided in a form of z-shaped incisions, such that triangularflaps formed by these incisions can be repositioned to allow expansionof the tissue with little or no gap being formed.

For example, micro-slits can be formed in a pattern of alternating linesof staggered micro-slits, where the gap between adjacent micro-slits ina line can be greater than about one-tenth ( 1/10th) of the length of anadjacent micro-slit, and where the spacing between adjacent lines ofmicro-slits can be between about ⅓ and 3 times the length of amicro-slit. Micro-slits can also be provided in other patterns, such asrandom arrays, circular or spiral patterns, or arrays containingorthogonal lines of micro-slits. According to another exemplaryembodiment of the present disclosure, an apparatus can be provided whichis configured to form micro-slits in a tissue. The exemplary apparatuscan include one or more blades, where each blade can further include oneor more extensions or protrusions, with each having a sharp cuttingedge. For example, the width of the extensions can correspond to theapproximate width of the micro-slits formed when each extension ispressed into the tissue.

In yet another exemplary embodiment, the apparatus can include a stackof such blades that can be spaced apart from one another by a particulardistance, e.g., using spacer elements between the blades. Such exemplaryapparatus can be used to form a plurality of micro-slits simultaneouslyusing a ‘stamping’ procedure, whereby the ends of the blades havingsharp cutting edges are pressed into the tissue and then withdrawn. Thisexemplary stamping procedure can be repeated in different locations onthe tissue to provide micro-slit meshing for a larger tissue area.

In a further exemplary embodiment of the present disclosure, a rollerapparatus can be provided that includes a plurality of extensionsprovided on one or more circular blades, where the circular blades areconfigured to rotate around an axle in a roller configuration. Theexemplary roller apparatus can optionally include a handle coupled tothe axle. The circular blades can be rolled over the tissue, and theextensions around the perimeter of the circular blades penetrate thetissue to form a plurality of micro-slits.

According to still another exemplary embodiment of the presentdisclosure, an apparatus can be provided which is configured to formmicro-lines in tissue using optical energy such as, e.g., an ablativelaser apparatus. The exemplary apparatus can include, for example, alaser source, a controller, and an optical arrangement. The laser sourcecan be an ablative laser such as a CO2 laser or the like. The controllercircuitry can be configured to control parameters of the laser sourceand of the optical arrangement, for example, to form a plurality ofmicro-slits in the tissue by direct energy from the laser source toablate thin regions of the tissue to a particular depth. According toyet another exemplary embodiment of the present disclosure, an apparatusfor facilitating an expansion of a biological tissue can be provided. Inparticular, a plurality of cutting arrangements can be provided, witheach cutting arrangement comprising at least one cutting edge structuredto cut at least one respective micro-slit in the tissue. For example, alength of extension of the cutting edge(s) of at least one of thecutting arrangements can be less than about 2 mm or less than about 1.5mm (or possibly less than about 1 mm or 0.8 mm). In addition, each ofthe cutting edge(s) of each of the cutting arrangements can comprises aplurality of cutting edges that have a length of extension that is lessthan about 2 mm or less than about 1.5 mm (or possibly less than about 1mm or 0.8 mm).

According to another embodiment, a method for forming micro-slits in atissue is provided. The method includes applying to the tissue: a rollerapparatus coupled to an axle and a plurality of extensions adapted toprotrude so that, when the apparatus is rolled over the tissue, theextensions can penetrate the tissue and simultaneously generate one ormore lines of micro-slits in the tissue.

These and other objects, features and advantages of the presentdisclosure will become apparent upon reading the following detaileddescription of exemplary embodiments of the invention, when taken inconjunction with the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

Further objects, features and advantages of the present disclosure willbecome apparent from the following detailed description taken inconjunction with the accompanying figures showing illustrativeembodiments, results and/or features of the exemplary embodiments of thepresent disclosure, in which:

FIG. 1A is an illustration of a first exemplary pattern of micro-slitsthat can be used to expand tissue in accordance with the presentdisclosure;

FIG. 1B shows an illustration of the pattern of the micro-slits of FIG.1A after the tissue has been expanded to form a plurality of small gapsin the tissue;

FIG. 2 is an illustration of a portion of the micro-slit pattern shownin FIG. 1A;

FIG. 3 is an illustration of a second exemplary pattern of themicro-slits that can be used to facilitate the tissue expansion;

FIG. 4 is an illustration of a third exemplary pattern of themicro-slits that can be used to facilitate the tissue expansion;

FIG. 5A is an illustration of a fourth exemplary pattern of themicro-slits that can be used to facilitate tissue expansion;

FIG. 5B illustrates a fifth exemplary pattern of the micro-slits thatcan be used to facilitate the tissue expansion;

FIG. 6A is an illustration of an exemplary z-shaped micro-incision thatcan be used to facilitate the tissue expansion;

FIG. 6B shows an illustration of the exemplary z-shaped micro-incisionof FIG. 6A after two triangular flaps have been transposed to provide anet lengthening of the tissue in a particular direction;

FIG. 7A is an illustration of a first exemplary array of z-shapedincisions that can be used to facilitate tissue expansion;

FIG. 7B is an illustration of a second exemplary array of z-shapedincisions that can be used to facilitate the tissue expansion;

FIG. 7C is an illustration of a third exemplary array of z-shapedincisions that can be used to facilitate the tissue expansion;

FIG. 8A is an illustration of a first exemplary blade configuration thatcan be used to form the micro-slits;

FIG. 8B is an illustration of a second exemplary blade configurationthat can be used to form the micro-slits;

FIG. 8C is an illustration of a third exemplary blade configuration thatcan be used to form the plurality of micro-slits;

FIG. 9 is an illustration of an exemplary stack of blades that can beused to form a plurality of micro-slits;

FIG. 10 is an illustration of an exemplary spiral blade configurationthat can be used to form the micro-slits;

FIG. 11A is an illustration of a first exemplary roller apparatus thatcan be used to form the micro-slits;

FIG. 11B is an illustration of a second exemplary roller apparatus thatcan be used to form the micro-slits;

FIG. 12A is an illustration of a first exemplary square pattern ofcutting edges that can be used to form the micro-slits in a tissue;

FIG. 12B is an illustration of a second exemplary square pattern of thecutting edges that can be used to form the micro-slits in the tissue;

FIG. 12C is an illustration of an exemplary pattern of the micro-slitsthat can be formed in a tissue using the square patterns of cuttingedges shown in FIGS. 12A and 12B;

FIG. 13A is an illustration of an exemplary hexagonal pattern of cuttingedges that can be used to form the micro-slits in the tissue;

FIG. 13B is an illustration of an exemplary pattern of the micro-slitsthat can be formed in the tissue using the hexagonal pattern of thecutting edges shown in FIG. 13 A;

FIG. 14 is a schematic illustration of an exemplary laser apparatus thatcan be used to form the micro-slits in accordance with exemplaryembodiments of the present disclosure;

FIG. 15A is an image of an exemplary blade that can be used to form themicro-slits;

FIG. 15B is a further image of the exemplary blade shown in FIG. 15A;

FIG. 16A is a first image of an exemplary apparatus that can be used toform the micro-slits to facilitate tissue stretching in accordance withembodiments of the present disclosure;

FIG. 16B is a second image of a portion of the apparatus shown in FIG.16A;

FIG. 16C is a third image of a portion of the apparatus shown in FIG.16A;

FIG. 16D is a fourth image of a portion of the apparatus shown in FIG.16A, showing the pattern of the cutting edges;

FIG. 17A is an image of a piece of graft skin tissue that includes themicro-slits provided therein in accordance with the exemplaryembodiments of the present disclosure;

FIG. 17B is an image of the piece of the graft skin tissue shown in FIG.17A after such skin tissue has been stretched;

FIG. 18A is an illustration of an exemplary pattern of the micro-slitsthat can be used to expand tissue in situ in accordance with the presentdisclosure; and

FIG. 18B is an illustration of the in situ tissue shown in FIG. 18Aafter such tissue has been stretched.

Throughout the drawings, the same reference numerals and characters,unless otherwise stated, are used to denote like features, elements,components, or portions of the illustrated embodiments. Moreover, whilethe present disclosure will now be described in detail with reference tothe figures, it is done so in connection with the illustrativeembodiments and is not limited by the particular embodiments illustratedin the figures. It is intended that changes and modifications can bemade to the described embodiments without departing from the true scopeand spirit of the present disclosure as defined by the appended claims.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments of the present disclosure provide method andapparatus for facilitating tissue expansion by forming a plurality ofmicro-slits in the tissue, where each micro-slit is sufficiently smallsuch that it may not be easily seen by the human eye withoutmagnification. By providing a plurality of such small micro-slits in atissue, it is possible to utilize a procedure that can be referred to as“micro-meshing,” such that the gross appearance of the tissue (e.g.,skin) when expanded may remain substantially normal after healing.Accordingly, such exemplary micro-meshing procedure can be used in situ,for example, in place of other conventional techniques, such asadvancement flaps or skin tension release operations, which can be moreproblematic. Exemplary embodiments of the present disclosure can alsoprovide ways to eliminate a need for a tissue graft in certainapplications by facilitating a stretching of adjacent tissue in situthat can exhibit a substantially normal appearance after healing.

According to a first exemplary embodiment of the present disclosure, amethod can be provided for facilitating tissue stretching by forming aplurality of micro-slits in full or partial thickness tissue such as,e.g., skin or other connective tissue. The size, orientation, density,and configuration of the micro-slits can be selected to facilitate acertain amount of tissue expansion for a particular application asdescribed herein. Such micromesh tissue expansion can be accomplished insitu, e.g. by providing micro-slits in skin tissues adjacent to or atsome distance from a local wound that needs to be closed, to facilitatestretching of the skin tissue over the wound. Such exemplary method canalso be used, e.g., to facilitate the expansion of graft tissues, suchas a piece of skin harvested from a donor site that can be used to covera wound.

An exemplary array 100 of micro-slits is shown in FIG. 1A. Thisexemplary micro-slit array 100 has a form of staggered rows of collinearslits. Such array can be used, e.g., to facilitate a substantiallyunidirectional expansion of the tissue in the direction of arrow 110.FIG. 1B illustrates the exemplary array 100 after it has been stretched.Each micro-slit has widened to form a small lens-shaped gap thatfacilitates the overall tissue length to increase in the direction ofthe arrow 110 without significant contraction in the perpendiculardirection along the tissue surface. These small gaps may rapidly fill inwith the regrown tissue as the stretched tissue heals.

For example, the length of the micro-slits can be less than about 2 mm,or less than about 1.5 mm, to avoid a likelihood of forming visiblescars and/or to allow a rapid regrowth of the gaps formed in theexpanded micro-slits. The length of the micro-slits can be less thanabout 1 mm, or less than about 0.8 mm. The length of each micro-slit canbe greater than about 0.1 mm to facilitate a sufficient expansion of thetissue using a reasonable number of slits. In general, a maximum widthof the gap formed by each micro-slit when the tissue is expanded ispreferably less than about 1.5 mm. This width of the gaps can also beless than about 1.0 mm, or less than about 0.5 mm.

Small micro-slits as described herein can provide several advantagesover conventional meshing techniques. For example, each of themicro-slits can be a tissue wound that forms a gap when the tissue isexpanded. This gap may eventually be filled in by a wound healingprocess. Clinical experience indicates that very small wounds may healby regrowth of healthy tissue, a process that can be referred to asremodeling, with little or no scar tissue formation. During tissueremodeling, local structures such as hair follicles, sebaceous and sweatglands are capable of local regeneration when injured on the scale ofthe structure itself, e.g., at distances of less than about 1 mm.Examples of tissue injury that can be healed by remodeling include,e.g., tattoo placement (which may involve a healing of thousands ofmicroscopic puncture wounds), and healing of single puncture woundscreated by insertion of hypodermic needles or the like.

In contrast, large wounds may heal by replacement of damaged or losttissue with undesirable scar tissue. Scar tissue can re-establishphysical integrity, but it often can be dysfunctional. In skin, scartissue lacks hair follicles, sweat glands, and normal dermal anddermo-epidermal junction structure. Scar tissue can also be mechanicallystiff as compared with healthy tissue. Over time, scars subjected totension may react by contraction. This response can be observed afterburn trauma and surgery, and can be debilitating. Accordingly, usingmicro-slits having a size smaller than that used in conventional tissuemeshing, e.g., less than about 2 mm or less than about 1.5 mm in length,can facilitate a prevention of a formation of significant amounts ofscar tissue after the stretched tissue heals. Further, generatingmicro-slits having a length that is smaller than that of a diameter ortypical spacing of major skin arteries can facilitate a meshing of thetissue that may not fully or substantially sever its blood supply.Healing of the gaps created in the expanded tissue after micro-meshingcan also occur more rapidly than healing of larger gaps created usingconventional meshing techniques, because of the smaller distances andareas of regrowth that occur, supported by adjacent healthy tissue.

Using a small micro-slit size for tissue expansion, especially in skin,can provide further advantages, e.g., in the appearance of the tissueafter expansion and healing. Even if a small amount of scar tissue formsin each micro-mesh incision, a grossly visible scar can be avoided. Suchmicro-slits can create small “dells” in the skin surface after healingthat can effectively disappear among normal dermatoglyphics (e.g.,permanent skin surface texture features). An ability to visually resolvea skin feature can depend on a size of the feature, and a distance fromwhich it is viewed. The micro-meshing procedure performed in accordancewith the exemplary embodiments of the present disclosure can beperformed using a plurality of micro-slits, each of which can beapproximately at or below the resolution of human vision under typicalviewing conditions, e.g., from a distance of about 0.5 meter.

As an example of this visual effect, newsprint photographs can becomposed using individual ink spots having feature sizes that are belowthe resolution limit of the naked eye when viewed at typical distances.Such photographs can be formed, for example, using small dots of inkspaced about 0.5 mm apart in a simple array. Although all points on thephotograph can be either white (e.g., spaces between ink dots) or black(e.g., points within an ink dot), the photograph may appear as a fullgray-scale range to the naked eye because the ink dots are notindividually resolved. The size of each ink dot can be varied from zeroto completely intersecting with its neighbors, which can produce whiteand black regions, respectively. A full gray scale can be obtained forportions of the array containing intermediate-sized dots.

An appearance of such newsprint photographs as apparently continuouslyvarying shades of gray can be analogous to skin appearance aftermicro-meshing, in which a uniform appearance can be obtained despite thepresence of very small regions of the regrown tissue. An exemplary sizerange for micro-slits cut into tissue to facilitate tissue expansion canbe somewhat greater than that for typical newsprint photographs, becausethere can be a lower contrast between the original and the regrowntissue as compared to the contrast between the white paper and black inkdots.

Using small micro-slit and gap sizes as described herein for tissueexpansion facilitated by the exemplary micro-meshing procedure can alsofacilitate rapid healing after the tissue is stretched. The healing timefor a gap in the tissue can be approximately proportional to the size ofthe gap. For example, during fractional laser ablative resurfacing ofskin, a large number of small holes (e.g., each hole being about 0.2 mmdiameter and 2 mm deep) can be produced, removing up to about 50% of theskin tissue. Within several days the epidermis can cover each hole, andwithin a week the holes can be filled in by remodeling without scarring.Similar rapid healing can be obtained in tissue stretching by forming aplurality of micro-slits in the tissue, such that the size of the gapformed by each micro-slit after stretching remains small.

The depth of the micro-slits can be sufficiently large to pass throughan entire thickness of a tissue graft (e.g., for an ex vivo tissuesample) or the tissue layer or structure (e.g., for in situapplications) to be expanded. For example, split-thickness skin graftscan typically be about 0.2 mm thick, and micro-slits used for expandingsuch grafts can be sufficiently deep to pass entirely through thisthickness. The micro-slits can also be formed in full-thickness grafts,e.g., that pass through the entire thickness of such grafts. Themicro-slits having a shallower depth can also be formed. For example,the micro-slits can be formed that have a depth of less than about 0.6mm in skin tissue, or less than about ⅓ of the total skin thickness. Themicro-slits having such depths can facilitate healing of the tissueafter such tissue is stretched while avoiding significant scar formationas described, e.g., in Plastic Reconstructive Surgery, vol. 119, pp.1722-32 (2007).

Micro-mesh expansion of other connective tissue such as tendon, earcartilage, etc., can be done using various micro-slit depths that can beselected based on mechanical properties of the tissue and the amount ofstretching desired. Tissue expansion can also be accomplished in threedimensions for organ tissues such as kidney, heart, and liver by formingappropriate micro-slits in various orientations, e.g., in at least oneof the xy, yz, and/or xz planes. The exemplary micro-slit array 100shown in FIG. 1A can be used to facilitate tissue expansion that can besubstantially unidirectional. The exemplary array 100 can be provided asa plurality of substantially parallel dashed lines, where each dash canrepresent a micro-slit formed in the tissue. The micro-slits can be in astaggered alignment, such as that shown in FIG. 1A, which may facilitatea substantially uniform unidirectional expansion of the tissue when anappropriate force is applied, as shown in FIG. 1B. Some staggering oroffset of the micro-slits in some rows of slits, e.g., in adjacent rows,can be provided such that any imaginary line drawn across the tissuesubstantially in the direction of expansion 110 can intersect aplurality of micro-slits that can widen by forming gaps in a directionsubstantially parallel to the arrows. Such staggering or offset of slitlines can thereby help to avoid formation of continuous regions ofun-slit tissue along the elongation direction, where such regions wouldlack gap-forming slits to accommodate the overall expansion and therebycan be undesirably strained.

A portion 200 of the exemplary micro-slit array 100 is shown in FIG. 2 .Parameters which can be used to describe the exemplary micro-slit arrayinclude, e.g., a micro-slit length 210, a gap length between adjacentmicro-slits 220, a spacing 230 between adjacent lines of micro-slits,and an overlap 240 between neighboring micro-slits in adjacent rows. Thegap length 220 can be at least about 1/10 of the micro-slit length 210.This exemplary ratio can provide sufficient tissue between adjacentmicro-slits to maintain integrity of the tissue when it is stretched.The spacing 230 between adjacent lines of micro-slits can be betweenabout ⅓ and 3 times the length of the adjacent micro-slits. Spacings 230that are smaller than this ratio range can reduce the mechanicalintegrity of the tissue when stretched, and spacings larger than thisratio range may not facilitate a sufficient expansion of the tissue.

The overlap 240 between neighboring micro-slits in adjacent rows can bebetween about 1/10 and 8/10 of the length of adjacent micro-slits. Thelarger overlap can provide a gap length 220 of at least about 1/10th ofthe adjacent micro-slit length 210 to be maintained between adjacentmicro-slits in a line. An overlap 240 of, e.g., at least 1/10th of theadjacent micro-slit length 210 can be effectuated so that there are noextended regions of tissue in the direction of the tissue expansion thatare free of any expandable micro-slits. Such extended micro-slit-freeregions, if present, can be subjected to excessive strains and possiblytear because there are no micro-slits available locally to form gaps andaccommodate the overall tissue expansion.

In addition to the exemplary micro-slit array 100 shown in FIG. 1A,which can provide unidirectional expansion of tissue, other slitarrangements can be provided to facilitate various expansion behaviorswhile maintaining small micro-slit and gap sizes as described herein.For example, micro-slit configurations similar to the array 100 shown inFIG. 1A can be used, where the slit lengths, the spacing betweenadjacent lines, and/or the spacing between slits in a single line can bevaried. Generally, a portion of tissue having closely-spaced lines ofmicro-slits can be stretched more than a portion having similar lines ofslits spaced further apart. Line spacings can thus be varied in such anarray to provide portions of tissue that can be stretched to varyingdegrees within a single graft or skin region. Certain further portionsof the tissue being stretched can also be free of any micro-slits toinhibit stretching in these portions. Such variations in a localexpandability can be used to provide improved cosmetic appearance of thestretched tissue or applied graft, e.g., based on such factors as hairfollicle density, pigmentation, etc.

Exemplary embodiments of the present disclosure can also facilitate fora use of tissue having an exemplary configuration or array ofmicro-slits 300 such as that shown in FIG. 3 , which includesintersecting lines of micro-slits that lie substantially along one oftwo substantially orthogonal directions. Such array of slits 300 can becapable of facilitating expansion of the tissue in any direction. Forexample, an arbitrary direction for stretching can generally beexpressed as a vector combination of two orthogonal stretchingcomponents that can be perpendicular to the two orthogonal slitdirections. Stretching of the tissue in a direction orthogonal to eachline of micro-slits can be accommodated by facilitating the micro-slitsto form gaps in that direction as shown in the exemplary embodiment ofFIGS. 1A and 1B. Thus, regular micro-slit arrays, such as the exemplaryarray 300 shown in FIG. 3 , can be used to provide grafts or regions ofin situ tissue that can be more easily expanded in any direction.

The exemplary micro-slits described herein can also be used to stretchskin in situ, e.g., to cover certain wounds or damaged skin regions withtissue from adjacent healthy regions. An exemplary illustration of suchin situ stretching procedure is shown in FIGS. 18A and 18B. For example,a plurality of micro-slits 1220 can be formed in a healthy tissue 1800that is adjacent or proximal to a wound 1810. For example, the wound1810 can be a portion of the tissue where an outer layer of the skin ismissing, e.g., a portion of the skin surface that may have been burnedor abraded. The wound 1810 can be cleaned to remove any remainingportions of the damaged tissue and/or to provide a uniform and sterilebase of tissue capable of receiving an overlayer of stretched tissue.

The exemplary micro-slits 1220 shown in FIG. 18A can be formed such thata surface direction of the micro-slits 1220 is substantiallyperpendicular to the direction that the healthy tissue 1800 is to bestretched. A local density of the micro-slits 1220 can also be higher inregions of the healthy tissue 1800 that is to be stretched further,e.g., those regions that are to undergo a greater areal expansion tocover the wound 1810. FIG. 18B shows an exemplary illustration of thehealthy tissue 1800 shown in FIG. 18A after such tissue has beenstretched to cover the wound 1810. The micro-slits 1220 can be formed asdescribed herein, and can be provided in a sufficient density that a gap1820 formed by each stretched micro-slit is small, e.g., less than about1.5 mm in width, or less than about 1 mm in width. Such small gaps 1820can facilitate a rapid healing of the stretched tissue 1800, and canavoid a formation of visible scars.

The healthy skin tissue 1800 can be about 1-3 mm thick. The micro-slits1220 that are formed to facilitate the expansion of this skin tissue1800 in situ can be provided at least to a depth so as to extend throughsubstantially the entire local dermal layer. For example, the dermallayer of the skin 1800 may not be strongly attached to the fatty layerbelow, such that the skin 1800 can more easily separate from theunderlying fatty layer, and be stretched to widen the gaps 1820 in themicro-slits 1220. The micro-slits 1220 formed in situ may, e.g., notextend into the underlying tissue below the dermis to any significantdepth, to avoid damaging blood vessels and/or other structuresunderlying the skin tissue 1800.

In further exemplary embodiments, micro-slit arrays can be formed usingmicro-slits oriented in a plurality of directions, such as in theexemplary micro-slit array 400 shown in FIG. 4 . The micro-slits can beformed in a pattern which may repeat at some distance, or theirpositions and/or orientations can be random. The exemplary array 400shown in FIG. 4 can be used to facilitate the expansion of portions ofthe tissue in different directions. The micro-slits can be provided in asubstantially non-intersecting pattern to reduce or avoid a formation ofwide gaps and/or pointed flaps of tissue after expansion is achieved byapplying appropriate tension to the micro-meshed tissue.

In still further exemplary embodiments, a circular micro-slit patternsuch as an exemplary pattern 500 shown in FIG. 5A can be used tofacilitate a particular expansion behavior of the tissue. The round slitpattern shown in FIG. 5 A can be used, for example, to facilitate theexpansion of a nominally flat piece of tissue over a rounded surfacesuch as, e.g., a chin or a shoulder. A micro-slit pattern that includesone or more spiral-shaped lines of slits, such as the exemplary pattern510 shown in FIG. 5B, can also be used to facilitate a similar tissueexpansion geometry.

Several exemplary parameters associated with the micro-slit arrays canbe varied for particular applications including, for example, averagemicro-slit length, variation of micro-slit lengths, slit density (e.g.,number of micro-slits per unit area of tissue), micro-slit orientations,spacing between micro-slits or lines of micro-slits (which can berelated to the overall micro-slit density), and/or randomness ofmicro-slit staggering. A mean orientation of a group or pattern of themicro-slits can be selected to better facilitate tissue expansion in oneor more particular directions. For example, if an expansion of thetissue is desired along a given vector, e.g., a primarilyone-dimensional expansion, most or all of the micro-slits can beoriented substantially perpendicular to that vector, as shown in FIG. 1. An omnidirectional tissue expansion can be facilitated, e.g., byproviding a plurality of micro-slits having a mean orientation vectorthat is nearly zero, e.g., as shown in FIGS. 3 and 4 .

In further exemplary embodiments of the present disclosure, micro-slitscan be provided to form a plurality of z-shaped micro-incisions 600,such as that shown in FIG. 6A. Such z-shaped micro-incisions can besimilar in shape to incisions used, e.g., in a conventional z-plastyprocedure as described, e.g., in Salam et al., American FamilyPhysician, vol. 67, no. 11 (Jun. 1, 2003), pp. 2329-2332. The exemplaryz-shaped micro-incisions 600 can include, e.g., two opposing micro-slits610, which can be substantially parallel or at some small angle relativeto each other, and a diagonal micro-slit 620 connecting near ends of theopposing micro-slits 610 to form two triangular flaps 630, 640.

The relative positions of the flaps 630, 640 can be switched across thediagonal micro-slit 620, e.g., as shown in FIG. 6B, which can facilitatea net expansion of the tissue in the direction 650 and a slightcontraction of the tissue in a direction substantially orthogonal tosuch direction 650. The micro-slits 610, 620 can be approximately thesame length to facilitate the alignment of the flaps 630, 640 after theyare repositioned as shown in FIG. 6B. Further, similar to conventionalz-plasty procedures, the diagonal micro-slit 620 may intersect each ofthe two micro-slits 610 at substantially the same angle, which can alsofacilitate the alignment of the flaps 630, 640 when they arerepositioned. This angle of intersection can be about 60 degrees orless, to avoid excessive local deformation of the tissue and tofacilitate repositioning of the flaps 630, 640. Smaller angles can alsobe used, and they may provide a smaller amount of expansion when theflaps 630, 640 are repositioned.

A plurality of such z-shaped micro-incisions 600 can be provided invarious arrays, such as the exemplary arrays shown in FIGS. 7A-7C. Thesize, orientation and/or spacing of the z-shaped micro-incisions 600 canbe varied to provide different local expansion behavior of the tissue.Each of the micro-slits 610, 620 can be less than about 2 mm in length,or optionally less than about 1 mm. These micro-slit lengths of thez-shaped micro-incisions can be larger than corresponding lengths ofsingle micro-slits, such as those shown in FIG. 1A. This is because muchof the effective tissue expansion can be accomplished geometrically witha z-shaped micro-incision, such that smaller gaps can be formed when thetissue is stretched.

The micro-slit lengths described herein can be smaller than typical slitsizes used in conventional z-plasty techniques, and they can provideseveral advantages. For example, using the micro-slits 610, 620 to forma small z-shaped micro-incision 600 can facilitate the repositioning ofthe flaps 630, 640 when applying a local tension to the tissuecontaining the micro-slits 610, 620. The flaps 630, 640 are likelysmaller relative to their thickness than larger conventional flaps, andtherefore they can be comparatively rigid and easier to repositionproperly.

The flaps 630, 640 can also be repositioned with little or noundermining of the tissue beneath them. In contrast, conventionalz-plasty techniques can require significant undermining of tissuebeneath the relatively large triangular flaps to provide them withsufficient mobility to be moved with respect to adjacent tissue and berepositioned. Further, the small z-shaped micro-incisions 600 canproduce relatively small markings of the tissue after the tissue isexpanded and healed that may not be apparent to the naked eye, andthereby likely avoid a formation of larger, more visible scars or tissuediscontinuities. The flaps 630, 640 formed by the micro-slits 610, 620can also avoid the use of stitches to hold them m place afterrepositioning, in contrast to some large flaps used in conventionalz-plasty procedures. In addition, the alignment of the flaps 630, 640does not have to be precise to obtain tissue expansion without formationof undesirable scars. For example, any gaps formed by the micro-slits610, 620 after the tissue expansion can also be small (for example, lessthan about 0.5 mm). As described herein, functional tissue canpreferentially regrow in such small gaps rather than scar tissue.

A general pattern of slits can produce the same relative expansion(expressed as a percentage or fraction of the original tissue lengths)at any size scale based on geometric similarity. For example, aparticular array of large slits may provide approximately a 30%expansion in a certain direction by formation of lens-shaped gaps. Ifthe size and spacings of the slits in the particular array are uniformlydecreased by half (e.g., by 50%), the resulting array can also produce a30% expansion by forming lens-shaped gaps having a similar shape. Inthis example, four times as many of the smaller slits can be providedper unit area (as compared with the large slits) to obtain thisexemplary 30% expansion in a particular portion of tissue. The largernumber of smaller slits is based on the 50% reduction in size scale,which doubles the number of slits per unit distance in each of twoorthogonal directions parallel to the tissue surface. These particularexemplary percentages merely illustrate the effect of changing the sizescale of a slit pattern. In general, miniaturizing a given pattern ofmesh slits can provide substantially the same degree of tissue expansionas a larger slit pattern when forming gaps from the slits which have ageometrically similar shape.

Reducing the size scale of a slit pattern also proportionally can reducethe physical width of the gaps formed by the slits for a particularamount of overall tissue expansion. Thus, by using a pattern ofmicro-slits to expand tissue as described herein, the width of each gapformed when the tissue is expanded can be small. In general, the gapwidth used in tissue expansion can be less than about half themicro-slit length, or less than about one-quarter of the micro-slitlength. Larger gap widths can also be used. For example, greaterexpansion can be achieved using a particular micro-slit pattern if thegap width approaches the length of the micro-slits. This can lead toformation of gaps that are more equiaxed in shape. Such wider gaps canalso be useful for tissue expansion, particularly if the micro-slitlength and gap width are small enough to allow tissue to regrow and fillin the gap without producing significant amounts of scarring ornonfunctional tissue.

In general, reducing the micro-slit size (or an average micro-slit sizein an array or pattern of micro-slits having different sizes) can reducethe size of the gaps formed when the tissue is expanded. The micro-slitscan be larger than some minimum size that are selectable, e.g., based onthe type of tissue, the thickness of the tissue layer being expanded,the ease of forming small micro-slits, etc. The micro-slits can extendthrough substantially the entire thickness of the tissue being expanded.This can lead to larger aspect ratios of depth to length if very shortmicro-slits are formed in relatively thick tissue layers. Such narrow,deep micro-slits may not readily facilitate the uniform tissue expansionbecause of possible non-uniformities in the depth direction.Accordingly, a length-to-depth ratio of a micro-slit can be greater thanabout 1:10, or possibly greater than about 1:5. Length-to-depth ratiosof about 1:2 can also be used, as can larger ratios.

Visible disfigurement associated with scars can result from a lack ofdermatoglyphics, e.g., the scar tissue can have a smooth, often glossysurface. A pattern or array of micro-slits as described herein can beformed on a visible scar to disrupt the surface texture of the scarafter healing, which can result in a dermatoglyphic appearance that ismore similar to that of normal skin.

In another exemplary embodiments of the present disclosure, a tissueexpansion apparatus can be provided that is configured to form aplurality of micro-slits in a layer of tissue to be expanded. For exvivo meshing of split thickness skin grafts, for example, the apparatuscan have a configuration similar to that of a conventional meshingdevice, except that the cutting surfaces are configured to formmicro-slits as described herein that are much shorter than the slitlengths produced by the conventional meshing devices.

In certain exemplary embodiments, the expansion apparatus can includeone or more micro-blades that can be pushed through a skin surface to adesired predetermined depth to form micro-slits. Exemplary micro-blades800, 810, 820 that can form such micro-slits are shown in FIGS. 8A-8C.The micro-blades 800, 810, 820 can include a plurality of extensions 830coupled at their proximal ends to a blade body 840. A cutting edge 850can be provided at a distal end of each extension 830 to facilitate apenetration of the extensions 830 into the tissue to form themicro-slits. For example, the micro-blade 800 can be produced by cuttingaway portions of a conventional razor blade or the like to form theplurality of extensions 830. Other manufacturing procedures can also beused. The extensions 830 can be very thin and the cutting edge 850 canbe very sharp, for example, similar to a razor blade or a scalpel.

The length of the extensions 830 can be approximately the same as thedepth of the tissue being expanded. For example, if tissue (such as ahalf-thickness graft) is being expanded ex vivo, the length of theextensions 830 can be about the same as or greater than the tissuethickness to facilitate the formation of the micro-slits that can passthrough the entire thickness of the tissue. The blades 800, 810, 820 canbe formed of stainless steel and/or any other suitable material, such asanother metal, a polymer, or silicon, and they may optionally bedisposable. The approximate depth of the micro-slits formed cancorrespond to the length of the extensions 830, because the blades 800,810, 820 can only penetrate the tissue until the lower edge of the bladebody 840 contacts the tissue surface. Alternatively or in addition, theextensions 830 that are longer than the desired depth of the micro-slitscan be provided. The depth of the micro-slits formed can be controlled,e.g., by providing one or more hilts or stops on the blades 800, 810,820 located a particular distance above the cutting edge 850corresponding to the desired micro-slit depth. Such hilt or stop can befixed to the blades 800, 810, 820, or alternatively it can be adjustableto facilitate the formation of the micro-slits having different depthswith a single blade arrangement. The blades 800, 810, 820 can be pressedinto the tissue to form a single line of the micro-slits, and thisexemplary procedure can be repeated to form an array containing aplurality of such lines of micro-slits, such as the array 100 shown inFIG. 1A.

According to further exemplary embodiments, an apparatus for formingmicro-slits can be provided that includes a stack 900 of blades 910 asshown, e.g., in FIG. 9 . The stack 900 of the blades 910 may include aplurality of blades 910 such as those described herein, with spacers 920provided between the blades 910. The blades 910 can be staggered suchthat the extensions 830 with cutting edges 850 are configured to createa micro-slit pattern, such as that shown in FIG. 1A or the like, whenthe lower portion of the stack 900 is pressed into the tissue. The stack900 of blades 910 can also be pressed onto a particular portion oftissue for a second time, with the blades 910 oriented in a seconddirection that is substantially orthogonal to a first direction of theblades 910, to produce a pattern of micro-slits, e.g., similar to thatshown in FIG. 3 .

Other blade configurations can be used to create particular micro-slitpatterns. For example, FIG. 10 shows a plan view of a spiral blade 1000which can be formed by bending the blade 910 into a spiral shape, andwhich may further include spacers 920 between portions of the spiral.The spiral blade 1000 can be used to form a spiral pattern ofmicro-slits such as that shown in FIG. 5B. Various micro-slit patternscan be obtained by using different combinations and configurations ofblades as described herein.

According to another exemplary embodiment of the present disclosure, anexemplary roller apparatus 1100 (such as that shown in FIG. 11A) can beprovided. For example, the roller apparatus 1100 can include a roundblade body 1110, with a plurality of substantially coplanar extensions830 provided around a perimeter of the circular blade body 1110. Acutting edge 850 can be provided on an outer portion of each extension830, and may optionally extend along a portion or all of the sides ofthe extensions 830. The blade body 1110 can be configured to rotatearound an axle 1140 that can be attached to a handle 1150. The exemplaryroller apparatus 1100 can be rolled over a portion of tissue to producea line of micro-slits. The exemplary roller apparatus 1100 can be used,for example, to easily form a large number of micro-slits over a largearea of tissue by rolling the apparatus 1100 across the tissue.

A further exemplary embodiment of a roller apparatus 1120 is shown inFIG. 11B. The exemplary roller apparatus 1120 can include a circularblade body 1110. A plurality of extensions 830 can be provided aroundthe perimeter of the circular blade body 1110, for example, in astaggered configuration. A cutting edge 850 can again be provided on anouter portion of each extension 830, and may optionally extend along tothe sides of the extensions 830. The blade body 1110 can be configuredto rotate around the axle 1140, which can be attached to a handle 1150.The roller apparatus 1120 can then be rolled over the tissue to producea plurality of lines of micro-slits at the same time, for example,similar to the array of micro-slits 100 shown in FIG. 1A.

The ease with which an exemplary cutting apparatus can form themicro-slits by cutting through tissue may depend on factors such as,e.g., a sharpness of each cutting edge 850, a width and/or thickness ofeach extension 830, a rigidity of the tissue, an applied pressure, anumber and/or density of the extensions 830, etc. It can be difficult toforce a high density of small extensions 830 into the tissuesimultaneously. Various modifications to the exemplary embodiments ofthe apparatus as described herein can be provided to facilitate aneasier formation of the micro-slits. For example, the extensions 830and/or cutting edges 850 can be coated with a lubricant or otherlow-friction coating. The extensions 830 can be inserted sequentiallyinto the tissue rather than simultaneously, such as with the rollerapparatus 1100.

The extensions 830 can also be driven into the tissue using forceimpulses, e.g., by tapping or hammering using piezoelectric elements,solenoids, pneumatics, hydraulics, etc. In certain embodiments, avibrating arrangement such as, e.g., a transducer can be mechanicallycoupled to the apparatus to induce vibrations in the extensions 830 andfacilitate their penetration into the tissue. For example, the vibrationcan be provided at frequencies up to about 100 kHz. Certain advantagesof the cutting devices over other techniques for forming slits in thetissue can include disposability, low cost, simplicity, ease of use, andeye-safe operation.

In further exemplary embodiments of the present disclosure, a micro-slitpattern can be formed that includes different parameters (e.g., slitlength, orientation, density, etc.) can be provided in different regionsof a single portion of tissue. For example, the micro-slit patterns suchas those shown in FIG. 1A can be provided at different orientations indifferent regions of the tissue. The local expansion of the tissue ineach region can be utilized in a direction substantially orthogonal tothe local micro-slits, as shown in FIG. 1B. Accordingly, a variation inmicro-slit parameters in a tissue portion can be used to furtheraccommodate variations in local expansion behavior of the stretchedtissue. For example, by varying micro-slit parameters, a particularsection of graft tissue can be expanded to better fill a wound areahaving a shape different than that of the unexpanded graft tissue. Sucha variation in micro-slit parameters can also be used to expand tissuein situ to better cover and conform to the shape of an adjacent woundarea.

For example, an exemplary apparatus for facilitating tissue expansioncan be provided that includes the extensions 830 arranged in anexemplary array 1200 that has an overall square or rectangular shape, asshown in FIG. 12A. A further exemplary array 1210 that can include theextensions 830 arranged in a diagonal direction is shown in FIG. 12B.For example, such exemplary arrays 1200, 1210 of extensions 830 can beformed using the stack 900 of the blades 910 as shown in FIG. 9 . Eachextension 830 can include, e.g., a cutting edge 850 provided on a distalportion thereof to facilitate the insertion of the extension 830 intothe tissue to form a micro-slit.

One or more apparati that includes such an array 1200, 1210 can bepressed into a plurality of regions of the tissue, for example, to forma pattern of the micro-slits such as the exemplary pattern(s) shown inFIG. 12C. The exemplary pattern(s) of micro-slits 1220 shown in FIG. 12Ccan include several regions outlined by dashed lines 1230, where eachregion can have a particular local orientation of the micro-slits. Theexemplary pattern(s) shown in FIG. 12C can thereby provide asubstantially uniform distribution of the micro-slits 1220 over aportion of tissue that includes a variation in local stretchingdirections (e.g., directions substantially orthogonal to the length of amicro-slit 1220). Providing the arrays 1200, 1210 in a substantiallysquare or rectangular shape, e.g., as shown in FIGS. 12A and 12B, canfacilitate the formation patterns of the micro-slits 1220 that aresubstantially uniformly spaced over a portion of tissue to be stretched.

In a further exemplary embodiment, an apparatus for facilitating tissueexpansion can be provided that can include a plurality of extensions 830arranged in an array 1300 that can have an approximately hexagonalshape, as shown in FIG. 13A. As described above with respect to thearrays 1200, 1210 of FIGS. 12A and 12B, the exemplary array 1300 canalso be formed, e.g., using the stack 900 of the blades 910 similar tothat shown in FIG. 9 . The lengths of the blades 910 can be selected toprovide the hexagonal array 1300 shown in FIG. 13A.

The apparatus that can include such array 1300 can be pressed into aplurality of regions of a tissue, for example, to form a pattern ofmicro-slits 1220 that can cover a portion of tissue to be stretched witha substantially uniform density of such micro-slits. For example, theexemplary pattern of micro-slits 1220 shown in FIG. 13B can includeseveral regions outlined by dashed lines 1310, where the micro-slits1220 in each region can be formed by pressing the array 1300 of theextensions 830 into the tissue, and withdrawing it. The exemplarypattern shown in FIG. 13B can be used to facilitate stretching of tissue(e.g., skin) over a rounded surface (e.g., an elbow, a chin, or thelike), similar to the circular pattern shown in FIG. 5A. Other uniformdistributions of the micro-slits 1220 having variations in localpreferred stretching directions can also be formed using the apparatusthat can include the exemplary array 1300 of the extensions 830 shown inFIG. 13A.

In a further exemplary embodiment, an apparatus that includes an arrayof the extensions 830 can be provided, e.g., in a form of a triangle oranother geometric shape, to facilitate formation of a pattern of themicro-slits 1220 that can have various local orientations thereof, andwhich can be used to provide a substantially uniform density ordistribution of the micro-slits 1220 over a portion of the tissue asdescribed above.

In still another exemplary embodiment, an optical apparatus 1400 asshown in FIG. 14 can be used to form a plurality of micro-slits asdescribed herein. The exemplary optical apparatus 1400 can include anoptical energy source 1410, an optical arrangement 1420, and a controlarrangement 1430. The optical energy source 1410 can be, e.g., anablative laser that is configured to produce minimal thermal injury,such as a pulsed CO2 laser, an Erbium (Er) laser, an excimer laser, orany one of various conventional femtosecond lasers. Other sources ofoptical energy that are configured to ablate or cut thin regions of thetissue can also be used.

For example, pulsed CO2 lasers and pulsed Er lasers that are commonlyused in dermatology and plastic surgery for tissue removal can generatea residual thermal damage layer in tissue next to an ablated region thatcan be between about 50 and about 200 micrometers in thickness. Excimerlasers, including a 193 nm excimer laser, can also be used and arecapable of cutting tissue with almost no observable residual thermaldamage. Such lasers are commonly used for LASIK procedures in cornealtissue. Femtosecond lasers, for example, having a pulse energy ofgreater than about 1 microjoule, when focused appropriately, can alsosever or ablate tissue while generating a negligible amount of thermaldamage in adjacent tissue. Such ablative lasers can operate atwavelengths and/or power densities for which the tissue exhibits strongoptical absorption. Exemplary advantages of using optical energy, e.g.,a laser, to form micro-slits in tissue as compared with blades or othermaterial cutting devices can include speed, precision, depth control,arbitrary micro-slit pattern design, sterility, and non-contactoperation.

The optical arrangement 1420 can include one or more waveguides, beamsplitters, and/or mirrors, and can be configured to direct energy fromthe optical energy source 1410 towards the tissue layer 1440 to form aplurality of the micro-slits 1220 therein. The control arrangement 1430can be configured to adjust parameters of the optical energy source 1410and the optical arrangement 1420 to affect and/or determine a position,length, and depth of the micro-slits 1220. The exemplary opticalapparatus 1400 can be provided in a fixed position relative to thetissue layer 1440. Alternatively, at least a portion of the opticalapparatus 1400 can be provided in or as a handpiece or the like, whichcan be translated or moved over the tissue layer 1440 to create largerregions of the micro-slits 1220.

EXAMPLE

Images of an exemplary blade in accordance with embodiments of thepresent disclosure are shown in FIGS. 15A and 15B. The exemplary bladeillustrated in FIG. 15A can be similar to the exemplary blade 800illustrated in FIG. 8A. A close-up view of the extensions provided onthe blade 800, each with a cutting edge at a distal end thereof, isshown in FIG. 15B.

Images of the exemplary apparatus in accordance with certain exemplaryembodiments of the present disclosure are shown in FIGS. 16A-16D. Theexemplary apparatus shown in FIG. 16A can include a handle attached toplurality of blades, where each blade is similar to the blade shown inFIG. 15A. FIGS. 16B and 16C are close-up images of the stack of bladeshaving spacers between them, similar to the stack of the blades 900shown in FIG. 9 . FIG. 16D provides an image of the array of cuttingedges provided by the exemplary apparatus, which can be used to form apattern of micro-slits that is similar, e.g., to the pattern of themicro-slits shown in FIG. 1A.

A piece of human graft skin tissue is shown in FIG. 17A. A portion ofthis tissue can include a pattern of micro-slits formed therein usingthe exemplary apparatus shown in FIGS. 16A-16D, in accordance with theexemplary embodiments of the present disclosure. The pattern ofmicro-slits can be similar to the exemplary pattern shown in FIG. 1A.

FIG. 17B illustrates an image of the skin tissue shown in FIG. 17A afterit has been stretched sideways. Each micro-slit can be widened to form asmall gap, and the portion of tissue that includes the pattern ofmicro-slits appears to have expanded substantially uniformly in aleft-right direction. This stretched pattern of gaps is similar to thatshown in FIG. 1B. A maximum dimension of each gap is small, e.g., on theorder of about a millimeter or less as described herein. Accordingly,the graft tissue may regrow to rapidly fill in these small gaps, e.g.,when the graft tissue is applied to a recipient site, and the healedgraft tissue may appear substantially normal because of the small sizescale of the plurality of healed gaps.

The foregoing merely illustrates the principles of the invention.Various modifications and alterations to the described embodiments willbe apparent to those skilled in the art in view of the teachings herein.It will thus be appreciated that those skilled in the art will be ableto devise numerous techniques which, although not explicitly describedherein, embody the principles of the invention and are thus within thespirit and scope of the invention. All patents, patent applications, andother publications cited herein are incorporated herein by reference intheir entireties.

What is claimed is:
 1. A method for forming micro-slits in a tissue, themethod comprising, applying to the tissue: a roller apparatus coupled toan axle; and a plurality of extensions protruding from the rollerapparatus so that, when the roller apparatus is rolled over the tissue,the plurality of extensions penetrate the tissue and simultaneouslygenerate a plurality of micro-slits in the tissue; each of the pluralityof extensions having a width that is approximate a length of amicro-slit formed within the tissue by the respective extension.
 2. Themethod of claim 1, wherein the plurality of extensions arecircumferentially spaced apart around the roller apparatus.
 3. Themethod of claim 2, wherein the plurality of extensions generate one ormore lines of micro-slits in the tissue facilitating unidirectionaltissue expansion.
 4. The method of claim 1, wherein the plurality ofextensions are provided in a pattern on the roller apparatus configuredto generate a pattern of micro-slits in the tissue facilitatingmultidirectional tissue expansion.
 5. The method of claim 4, wherein theplurality of extensions are provided in a random, non-intersecting,pattern on the roller apparatus to generate a random, non-intersecting,pattern of micro-slits in the tissue.
 6. The method of claim 1, whereinthe plurality of extensions are configured to form the micro-slitshaving a depth of less than about 0.6 mm.
 7. The method of claim 1,wherein the plurality of extensions are configured to form micro-slitshaving a depth of less than about one-third of a total skin thickness.8. The method of claim 1, wherein the width of at least one of theplurality of extensions is configured to form a micro-slit with a lengthof about 2 mm or smaller.
 9. The method of claim 1, wherein the width ofat least one of the plurality of extensions is configured to form amicro-slit with a length of about 0.8 mm or smaller.
 10. The method ofclaim 1, wherein each of the plurality of extensions incudes a cuttingedge at a distal end thereof.
 11. The method of claim 1, wherein theforming of micro-slits in tissue is performed in situ adjacent a woundin which tissue is absent and over which the tissue is to be stretched,the method further comprising: orienting the micro-slits in the tissueperpendicular to a direction in which the tissue is to be stretched. 12.A method for forming micro-slits in a skin tissue, the methodcomprising, applying to the tissue: a roller apparatus coupled to anaxle; and a plurality of extensions protruding from the roller apparatusso that, when the roller apparatus is rolled over the tissue, theplurality of extensions penetrate the tissue and simultaneously generatea plurality of micro-slits in the tissue, each micro-slit having a depthof less than about one-third of a total skin thickness.
 13. The methodof claim 12, wherein the forming of micro-slits in tissue is performedin situ adjacent a wound in which tissue is absent and over which thetissue is to be stretched, the method further comprising: orienting themicro-slits in the tissue perpendicular to a direction in which thetissue is to be stretched.
 14. The method of claim 13, wherein theplurality of extensions are circumferentially spaced apart around theroller apparatus.
 15. The method of claim 14, wherein the plurality ofextensions generate a plurality of lines of micro-slits in the tissuefacilitating unidirectional tissue expansion.
 16. The method of claim15, wherein a spacing between adjacent lines of micro-slits can bebetween about ⅓ and about 3 times a length of an individual micro-slitof the plurality of micro-slits.
 17. The method of claim 15, wherein theplurality of micro-slits are provided in the tissue in a density whereina gap formed by each stretched micro-slit is less than about 1.5 mm inwidth.
 18. The method of claim 17, wherein the gap formed by eachstretched micro-slit is less than about 1 mm in width.
 19. The method ofclaim 12, wherein the width of at least one of the plurality ofextensions is configured to form a micro-slit with a length of about 2mm or smaller.
 20. The method of claim 12, wherein the width of at leastone of the plurality of extensions is configured to form a micro-slitwith a length of about 0.8 mm or smaller.